Ancient adhesives raw material choices were limited. Starch, blood, and collagen extracts from animal bones and hides were early adhesives sources. Later, suitable raw materials used in adhesives expanded to include milk protein and fish extracts. These early starch and protein-based adhesives suffered from a number of drawbacks, including lack of durability and poor water resistance.
Adhesives based on protein-containing soy flour first came into general use during World War I. To obtain suitable soy flour for use in these early adhesives, some or most of the oil was removed from soybean, yielding a residual soy meal that was then subsequently ground into extremely fine soy flour. The soy flour was then denatured and, to some extent, hydrolyzed to yield adhesives for wood bonding under dry conditions. However, these early soybean adhesives suffered from the same drawbacks as other early protein-based adhesives, and their use was strictly limited to interior applications.
In the 1920's, phenol-formaldehyde (PF) and urea-formaldehyde (UF) adhesive resins were first developed. Phenol-formaldehyde and, less frequently, modified urea-formaldehyde resins were exterior-durable, but high raw materials costs at that time limited their use. World War II contributed to the rapid development of these adhesives for water and weather resistant applications, such as exterior applications. However, the low cost protein-based adhesives, mainly soy-based adhesives, continued to be used in many interior applications.
After World War II, the petrochemical industry invested vast sums of money in research and development to create and expand new markets for petrochemicals. Within several years, the once costly raw materials used in manufacturing thermoset adhesives became inexpensive bulk commodity chemicals. In the 1960's, the price of petrochemical-based adhesives had dropped substantially, such that they displaced nearly all of the protein-based adhesives from the market.